A well known method for thawing frozen pipes is to inject hot water into the pipe through a flexible tube, while advancing the tube through the pipe as the ice therein melts. A device employing this technique is shown in Mentel U.S. Pat. No. 325,002, "Thawing Machine".
With such devices there is a need constantly to renew the hot water supply and to dispose of the melt. Simpson U.S. Pat. No. 458,503 proposed to solve these problems by catching the melt in a receptacle and cycling it back to a hot water reservoir. However, this technique is messy and can only be used where the receptacle can be placed directly underneath the pipe; and cannot be used, for example, for substantially vertically oriented pipes, or where the space below the pipe is obstructed.
With each of the devices of Mentel and Simpson, it is usually required that water service to the frozen pipe be first shut off at the service gate. Also with each the injected hot water stream is directed substantially coaxially longitudinally of the pipe.